/Engine/Plugins/Editor/UVEditor/Source/UVEditorTools/Public/ToolTargets/UVEditorToolMeshInput.h
Get the unwrap vids corresponding to a given applied vid. These will be multiple if the vertex is a seam vertex and therefore has multiple UV elements associated with it.
void AppliedVidToUnwrapVids ( int32 AppliedVid, [TArray](API\Runtime\Core\Containers\TArray)< int32 > & UnwrapVidsOut )